// run: $exec < input
#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>

long long n, w;
std::vector<long long> da;

int main()
{
	std::ios::sync_with_stdio(false);
	std::cin >> n >> w;
	da.resize(2 * n);
	for (long long i = 0; i < 2 * n; i++)
		std::cin >> da[i];

	std::sort(da.begin(), da.end());
	double min1 = da[0], min2 = da[n] / 2.0;
	double power = std::min(min1, min2);
	std::cout << std::setprecision(8) << std::fixed << std::min(double(w), power * 3 * n) << '\n';
}

